Electrochemical oxidation of cycloalkenes and cycloalkanes to α,ω-dicarboxylic acids or ketocarboxylic acids and cycloalkanone compounds

Abstract

The present invention relates to a method for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemically oxidizing unsubstituted or at least monosubstituted mono- or polyunsaturated cycloalkenes and unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons in an electrolytic cell in the presence of inorganic or organic nitrates in a reaction medium in the presence of oxygen.

Description

Technical Field

[0001] The present invention relates to a method for producing an unsubstituted or at least monosubstituted α,ω-dicarboxylic acid or ketocarboxylic acid and an unsubstituted or at least monosubstituted cycloalkanone by electrochemically oxidizing an unsubstituted or at least monosubstituted mono-unsaturated or poly-unsaturated cycloalkene and an unsubstituted or at least monosubstituted saturated cycloaliphatic hydrocarbon in an electrolytic cell in a reaction medium in which oxygen is present, in the presence of an inorganic or organic nitrate.

Background Art

[0002] α,ω-dicarboxylic acids, ketocarboxylic acids and cycloalkanone compounds are important substrates in organic synthetic chemistry and are monomer components in polymer synthesis, and are thus highly relevant to industrial applications. Conventional methods for obtaining these substrates from cycloalkanes and cycloalkenes basically involve transition metal-catalyzed reactions and the use of chemical oxidants.

[0003] A method for electrochemically oxidizing a cycloalkane to the corresponding ketone has not yet been described. Only a few examples are known of the production of dicarboxylic acids / their methyl esters by electrochemical oxidative double bond cleavage of cyclooctene and cyclododecene (U. Baumer, Electrochimica Acta 2003, 4, pp. 489-495; U.-St. Baumer, H.J. Schafer, J. Appl. Electrochem. 2005, 35, pp. 1283-1292; D.D. Davis, D.L. Sullivan, Method for producing dodecanedioic acid, 1991 and US Patent Application Publication No. 5,026,461). The synthesis of dicarboxylic acids by oxidative double bond cleavage starts from pure cycloalkenes.

[0004] Furthermore, in these prior art processes, the corresponding carboxylic acid esters are often obtained by synthesis, so that the production of free carboxylic acids often requires an additional hydrolysis step that requires additional time and resources.

[0005] Increased material inputs, such as the use of expensive transition metals as electrocatalysts or electrode materials, or the use of chemical oxidizers, generate reagent waste, which may require costly and complex disposal or recycling. Furthermore, these processes, with their complex electrolyte systems and the use of additional oxidizers, require large amounts of material input overall, negatively impacting cost balance and process economics. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] U.S. Patent Application Publication No. 5026461 [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective of the present invention is to provide a sustainable and resource-saving method for producing α,ω-dicarboxylic acids and cycloalkanones. [Means for solving the problem]

[0008] This objective was achieved through the subject matter of the claims and the specification.

[0009] The present invention provides a method for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation. (a-1) A step of preparing at least one unsubstituted or at least one substituted monounsaturated or polyunsaturated cycloalkene, (a-2) A step of preparing at least one unsubstituted or at least one monosubstituted saturated alicyclic hydrocarbon, (b) A step of preparing at least one inorganic or organic nitrate, (c) A step in which an unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene prepared in step (a-1) and an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon prepared in step (a-2) are electrochemically oxidized in the presence of an inorganic or organic nitrate prepared in step (b) in an electrolytic cell in a reaction medium containing oxygen. This provides a method that includes this.

[0010] Surprisingly, it was found that the method according to the present invention allows for the electrochemical oxidation of cyclic alkenes in the presence of cyclic alkanes of the same ring size to obtain α,ω-dicarboxylic acids / ketocarboxylic acids.

[0011] The method of the present invention allows for the conversion of industrially obtained cycloalkenes (often containing a certain proportion of alicyclic hydrocarbons) into α,ω-dicarboxylic acids, and in the process, cyclic ketones that can be similarly used in industrial applications are obtained as further products. The method of the present invention can simplify industrially important processes and further optimize them from a sustainability perspective.

[0012] This invention makes it possible to achieve resource-saving and synthetically important oxo-functionalization of supplying raw material chemicals while significantly avoiding the use of environmentally harmful transition metals and oxidizing agents. Selective conversion to the desired product and effective utilization of the dual function of conductive salts and mediators significantly reduce the generation of expensive reagent waste. This invention enables an electrochemical synthesis route for aliphatic α, ω-carboxylic acids, ketocarboxylic acids and cycloalkanones by effective concentrated electrolysis in which both electrode reactions are useful for synthesis.

[0013] The method of the present invention has special features such as high selectivity, use of small amounts of auxiliary chemicals, use of electric current as an oxidizing agent, and the resulting generation of small amounts of waste.

[0014] Even more surprisingly, the method of the present invention has been found to be able to be carried out at normal pressure and temperature. This is equally advantageous in terms of energy efficiency and, consequently, environmental compatibility.

[0015] The method of the present invention may use monocyclic or bicyclic unsubstituted or at least one-substituted monounsaturated or polyunsaturated cycloalkenes. It is preferable to use unsubstituted or at least one-substituted monounsaturated or polyunsaturated monocyclic cycloalkenes, and particularly preferable to use unsubstituted or at least one-substituted monounsaturated monocyclic cycloalkenes. The position of the unsaturated bond may be intra-ring or extra-ring, with intra-ring unsaturated bonds being preferred.

[0016] The unsubstituted or at least monosubstituted monounsaturated or polyunsaturated monocyclic cycloalkenes used in the methods of the present invention may have, preferably, 5 to 12 carbon atoms, particularly preferably 6 to 12 carbon atoms, and very particularly preferably 8 to 12 carbon atoms in the ring system. These cycloalkenes may be monounsaturated or polyunsaturated, with monounsaturated cycloalkenes being preferred. Each of these cycloalkenes may be unsubstituted, monosubstituted, or polysubstituted. If monosubstituted or polysubstituted, it is preferable that they are substituted with one, two, three, four, or five substituents independently selected from the group consisting of methyl, phenyl, or benzyl. The phenyl or benzyl substituents themselves may be unsubstituted, or monosubstituted or polysubstituted with one, two, or three substituents independently selected from the group consisting of F, Cl, Br, and NO2.

[0017] The unsubstituted or at least monosubstituted monounsaturated or polyunsaturated bicyclic cycloalkenes used in the methods of the present invention may have, preferably, 7 to 18 carbon atoms, particularly preferably 7 to 12 carbon atoms, and very particularly preferably 7 to 10 carbon atoms in the ring system. These cycloalkenes may be monounsaturated or polyunsaturated, with monounsaturated cycloalkenes being preferred. Each of these cycloalkenes may be unsubstituted, monosubstituted, or polysubstituted. If monosubstituted or polysubstituted, it is preferable that they are substituted with one, two, three, four, or five substituents independently selected from the group consisting of methyl, phenyl, or benzyl. The phenyl or benzyl substituents themselves may be unsubstituted, or monosubstituted or polysubstituted with one, two, or three substituents independently selected from the group consisting of F, Cl, Br, and NO2.

[0018] If a monocyclic or bicyclic cycloalkene used in accordance with the present invention, or if its substituents include alkyl radicals having one or more carbon atoms in their side chains, the implementation of the method of the present invention may result in undesirable side reactions of these substituents.

[0019] The monocyclic cycloalkene is particularly preferably selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, and 1-phenylcyclohexa-1-ene. Particularly preferred bicyclic cycloalkenes may be selected from the group consisting of bicyclo[2.2.1]hepto-2-ene, α-pinene, and carene.

[0020] The method of the present invention may use monocyclic or bicyclic, preferably bicyclic, unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons. In the method of the present invention, the use of monocyclic alicyclic hydrocarbons is particularly preferred.

[0021] The monocyclic or polycyclic, particularly monocyclic or bicyclic saturated alicyclic hydrocarbons used in the methods of the present invention, may preferably have 5 to 18 carbon atoms in the ring system. Each of these alicyclic hydrocarbons may be unsubstituted, monosubstituted, or polysubstituted. If monosubstituted or polysubstituted, it is preferable that they are substituted with one, two, three, four, or five substituents independently selected from the group consisting of methyl, phenyl, or benzyl. The phenyl or benzyl substituents themselves may be unsubstituted, or monosubstituted or polysubstituted with one, two, or three substituents independently selected from the group consisting of F, Cl, Br, and NO2. If the alicyclic hydrocarbons used according to the present invention, or their substituents, include alkyl radicals having more than one carbon atom in the side chain, the implementation of the methods of the present invention may result in undesirable side reactions with these substituents.

[0022] The method according to the present invention particularly preferably uses an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon, which has 6 to 12 carbon atoms in the ring, preferably 8 to 12 carbon atoms in the ring, and is unsubstituted or monosubstituted or polysubstituted with 1, 2, 3, 4, or 5 substituents independently selected from the group consisting of methyl, phenyl, or benzyl. The method according to the present invention most particularly preferably uses a monocyclic saturated hydrocarbon that has 8 to 12 carbon atoms in the ring, and is unsubstituted or monosubstituted, disubstituted, or trisubstituted with methyl groups.

[0023] The saturated monocyclic hydrocarbon is most preferably unsubstituted and selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane, and more preferably selected from the group consisting of cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane, with cyclododecane being the most preferred.

[0024] It is particularly preferable that the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohexa-1-ene, bicyclo[2.2.1]hept-2-ene, α-pinene, and carene, and that the saturated alicyclic hydrocarbon is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane.

[0025] It is particularly preferable that the cycloalkene is cyclododecene and the saturated alicyclic hydrocarbon is cyclododecane.

[0026] In the method of the present invention, the preparation of at least one unsubstituted or at least one-substituted monounsaturated or polyunsaturated cycloalkene by step (a-1) and the preparation of at least one unsubstituted or at least one-substituted saturated alicyclic hydrocarbon by step (a-2) are preferably carried out in combination, and particularly preferably as a mixture. Therefore, for example, a precursor product from an industrial-scale process containing these two components can be used directly in the method according to the present invention.

[0027] In the method according to the present invention, the ratio of unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkenes to unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons may vary over a wide range.

[0028] The molar ratio of unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkenes is preferably 40 to 95 mol%, more preferably 45 to 55 mol%, and particularly preferably 47 to 53 mol%, based on the total amount of unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkenes used and unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons.

[0029] Similarly, the molar ratio of the unsubstituted or at least monosubstituted mono-unsaturated or poly-unsaturated cycloalkene, in each case, is more than 60 mol%, preferably more than 65 mol%, particularly preferably more than 70 mol%, based on the total amount of the unsubstituted or at least monosubstituted mono-unsaturated or poly-unsaturated cycloalkene and the unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

[0030] It is very particularly preferred to use cyclododecene as the cycloalkene and cyclododecane as the saturated alicyclic hydrocarbon in amounts of 90 - 95 mol% and 5 - 10 mol%, respectively, based on the total amount of cyclodecene and cyclodecane.

[0031] Step (b) of the method according to the invention involves the preparation of at least one inorganic or organic nitrate. This nitrate functions both as a conductive salt and as a mediator for the electrochemical oxidation process according to the invention. It is preferred to use an inorganic or organic salt of the general formula [cation + [NO3 - .

[0032] [cation + is Na + , K + , and ammonium ions having the general structure [R 1 R 2 R 3 R 4 N + (wherein R 1 , R 2 , R 3 and R 4 are each independently selected from the group consisting of C1 - C 16 alkyl, especially straight-chain or branched C1 - C8 alkyl). General structure (I):

[0033]

Chemical formula

[0034] (wherein R 1and R 2 This refers to linear or branched chains C1-C 18 Alkyls, particularly those consisting of linear or branched C1-C8 alkyls, are independently selected from the group, R 3 H and linear or branched chains C1-C 18 Alkyl groups, particularly those consisting of H and linear or branched C1-C8 alkyl groups, are selected. The imidazolium cation, General structure (II):

[0035] [ka]

[0036] (In the formula, R 1 C1~C 18 Alkyl, particularly selected from the group consisting of linear or branched C1-C8 alkyl groups, R 2 , R 3 and R 4 H and linear or branched chains C1-C 18 Alkyl groups, particularly H, and linear or branched C1-C8 alkyl groups, are independently selected. The pyridinium cation, and General structure [R 1a R 2a R 3a R 4a P + ](where R 1a , R 2a , R 3a , R 4a C1~C 16 A phosphonium ion of alkyl groups, particularly those independently selected from the group consisting of linear or branched C1-C8 alkyl groups. It is selected from the group consisting of the following.

[0037] When an imidazolium cation-based organic nitrate is used in the method of the present invention, the cation of general formula (I) is preferred, where R 1 and R 2 This refers to linear or branched chains C1-C 18Alkyls, particularly those consisting of linear or branched C1-C8 alkyls, are independently selected from the group, R 3 is hydrogen. Particularly preferred is the imidazolium cation of general formula (I), where R is 1 is methyl, and R 2 Is it ethyl, or R 1 is methyl, and R 2 Is it methyl, or R 1 is methyl, and R 2 It is butyl, and R 3 In both cases, it is hydrogen.

[0038] When a pyridinium cation-based nitrate is used in the method of the present invention, the cation of general formula (II) is preferred, where R 1 This refers to linear or branched chains C1-C 18 Alkyl, particularly linear or branched C1-C8 alkyl. Particularly preferred is the pyridinium cation of general formula (II), where R 1 This refers to linear or branched chains C1-C 18 Alkyl, particularly linear or branched C1-C8 alkyl, and radical R 2 , R 3 and R 4 Each of these is independently selected from the group consisting of linear or branched C1-C8 alkyl groups, and is preferably monosubstituted at the 2nd, 3rd, or 4th position, disubstituted at the 2nd, 4th, 2nd, 5th, or 2nd, 6th positions, or trisubstituted at the 2nd, 4th, and 6th positions.

[0039] In the method of the present invention, in principle, two or more of the above-mentioned nitrates may be used. Nitrates according to the present invention, in particular composition [R 1 R 2 R 3 R 4 N + ][NO3 - ] Organic ammonium nitrate salts, or composition [R 1a R 2a R 3a R 4a P + ][NO3 - It is preferable to use an organic phosphonium salt of ], and in particular composition [R1 R 2 R 3 R 4 N + ][NO3 - Organic ammonium nitrate salts of ] are preferred.

[0040] It is particularly preferable that the organic ammonium nitrate is tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate. It is particularly preferable that the organic phosphonium nitrate is tetra-n-butylphosphonium nitrate or methyltri-n-octylphosphonium nitrate. It is preferable that the organic imidazolium nitrate is 1-butyl-3-methylimidazolium nitrate.

[0041] The organic nitrate used in the method according to the present invention is most preferably tetra-n-butylammonium nitrate or methyltri-n-octylammonium nitrate.

[0042] The order in which the components used in the method according to the present invention are prepared may vary, as may the order in which the individual components are brought into contact with each other or with their respective reaction media.

[0043] In one embodiment of the method according to the present invention, an unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene and an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon are first added, combined with a reaction medium, preferably partially or completely dissolved in the reaction medium or mixed therein, and then an inorganic or organic nitrate is added.

[0044] In another embodiment of the method according to the present invention, an inorganic or organic nitrate is first added and combined with the reaction medium, preferably partially or completely dissolved in the reaction medium or mixed in the reaction medium, and then an unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene and an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon are preferably added in combination.

[0045] Similarly, it is also possible to initially add an unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene, an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon, and an inorganic or organic nitrate, and then combine them with the reaction medium, preferably at least partially or completely dissolving them in the reaction medium or mixing them with the reaction medium. Furthermore, in the method of the present invention, it is also possible to add an unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene, an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon, and an inorganic or organic nitrate to the reaction medium and simultaneously or successively dissolve them in the reaction medium, preferably at least partially or completely dissolving them in the reaction medium or mixing them with the reaction medium.

[0046] The reaction medium used in the method of the present invention is a liquid under the conditions under which the method is carried out and can partially or completely dissolve the components used, i.e., particularly unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons and inorganic or organic nitrates. When at least one of these components is used in liquid form, the reaction medium is preferably readily miscible with the above components.

[0047] The method of the present invention uses a polar aprotic reaction medium for electrochemical oxidation. This can be used in anhydrous form, dry form, or in combination with water.

[0048] When inorganic nitrates, particularly potassium nitrate or sodium nitrate, are used in the method of the present invention, the reaction medium is preferably an aprotic reaction medium containing water and combined with water. The water content in the reaction medium can vary. In any case, the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume, and even more preferably up to 5% by volume, relative to the total volume of the reaction medium.

[0049] The polar aprotic reaction medium is preferably selected from the group consisting of aliphatic nitriles, aliphatic ketones, alicyclic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, dimethyl sulfoxides, esters and ethers, or at least two combinations of these components.

[0050] The reaction medium is preferably selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, γ-butyrolactone, and ε-caprolactone, or at least two combinations of these components.

[0051] The reaction medium is very preferably selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, dimethyl carbonate, and acetone, or at least two combinations of these components.

[0052] The reaction medium is very preferably acetonitrile, isobutyronitrile, or adiponitrile in dry or anhydrous form.

[0053] The reaction medium is very preferably acetonitrile, isobutyronitrile, or adiponitrile, similarly mixed with water as needed.

[0054] When one or more of the above components are used in combination with water in the reaction medium, the water content is preferably a maximum of 20% by volume, particularly preferably a maximum of 15% by volume, particularly preferably a maximum of 10% by volume, and even more preferably a maximum of 5% by volume, relative to the total volume of the reaction medium.

[0055] To carry out the method according to the present invention, it may be advantageous to add further solubilizing components to the reaction medium. Suitable advantageous components can be identified by simple preliminary tests of their dissolution behavior.

[0056] Examples of solubilizing components include primary alcohols, secondary alcohols, monoketones or dialkyl carbonates, or mixtures of at least two of these components, which are used in combination with water as needed. The method of the present invention is preferably C 1-6 Alcohols may be used. Particularly preferred solubilizing components are selected from the group consisting of methanol, ethanol, isopropanol, 2-methyl-2-butanol, or a mixture of at least two of these components, and may be used in combination with water as needed.

[0057] The reaction medium used is preferably dimethyl carbonate, and optionally at least one C 1-6 It may be used in combination with alcohols, particularly those selected from the group consisting of methanol, ethanol, isopropanol, and 2-methyl-2-butanol, and, if necessary, with water.

[0058] When one or more of these solubilizing components are used in combination with water, the water content is preferably up to 20% by volume, particularly preferably up to 15% by volume, very particularly preferably up to 10% by volume, and even more preferably up to 5% by volume, relative to the total amount of the solubilizing components and water.

[0059] In all cases, the solubilizing component may be added in an amount of less than 50% by volume, more preferably less than 30% by volume, and very preferably less than 10% by volume, relative to the total amount of the reaction medium.

[0060] In the method according to the present invention, the inorganic or organic nitrate is preferably used in an amount of 0.1 to 2.0 equivalents, preferably 0.2 to 1.0 equivalents, particularly preferably 0.3 to 0.8 equivalents, and very preferably 0.4 to 0.8 equivalents, relative to the amount of unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene used, and in an amount of 0.8 to 10.0 equivalents, preferably 2.5 to 10.0 equivalents, particularly preferably 3.0 to 10.0 equivalents, and very preferably 5.0 to 10.0 equivalents, relative to the amount of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

[0061] According to the present invention, the electrochemical oxidation of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons is carried out in an electrolytic cell in a reaction medium containing oxygen, in the presence of an inorganic or organic nitrate.

[0062] Therefore, an oxygen-containing gas atmosphere is advantageously provided in spatial communication with the reaction medium.

[0063] The proportion of oxygen in the gas atmosphere can vary. Preferably, the proportion of oxygen in the gas atmosphere is 10% to 100% by volume, particularly preferably 15% to 30% by volume, particularly preferably 15% to 25% by volume, and particularly preferably 18% to 22% by volume.

[0064] In one embodiment, the proportion of oxygen in the gas atmosphere may be 10% to 100% by volume, particularly preferably 15% to 100% by volume, and particularly preferably 20% to 100% by volume.

[0065] This is particularly advantageous when the gas atmosphere is air.

[0066] Gas exchange between the gas atmosphere and the reaction medium is preferably carried out by introducing the gas atmosphere into the reaction medium or by stirring the liquid phase in the presence of the gas atmosphere.

[0067] Gas exchange between the gas atmosphere and the reaction medium, particularly stirring, can be used to control electrochemical oxidation, for example, by adjusting the shape or speed of the stirrer.

[0068] The amount of oxygen dissolved in the reaction medium is preferably at least 1 millimoles, and particularly preferably at least 5 millimoles, per liter of reaction medium.

[0069] Similarly, the amount of oxygen dissolved in the reaction medium is preferably at least 10 millimoles per liter of reaction medium.

[0070] The present invention provides a method for producing unsubstituted or at least monosubstituted α,ω-dicarboxylic acids or ketocarboxylic acids and unsubstituted or at least monosubstituted cycloalkanones by electrochemical oxidation of an unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene with an unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon in an electrolytic cell in an oxygen-containing reaction medium, in the presence of an inorganic or organic nitrate. This method may be carried out in either a segmented electrolytic cell or a non-segmented electrolytic cell, and is preferably carried out in a non-segmented electrolytic cell.

[0071] A non-divided electrolytic cell preferably used in accordance with the present invention comprises at least two electrodes. For this purpose, anodes and cathodes made of conventional materials, such as glassy carbon, boron-doped diamond (BDD), or graphite, may be used. The use of glassy carbon electrodes is preferred.

[0072] A non-divided electrolytic cell is preferably provided with at least one glassy carbon anode or at least one glassy carbon cathode. It is preferable that both the anode and cathode are glassy carbon electrodes.

[0073] The distance between electrodes can vary over a specific range. The distance is preferably 0.1 mm to 2.0 cm, particularly preferably 0.1 mm to 1.0 cm, and most preferably 0.1 mm to 0.5 cm.

[0074] The method according to the present invention may further be carried out in a batch or continuous manner, preferably in a non-divided flow-through electrolytic cell.

[0075] In all cases, the method according to the present invention is preferably carried out with a charge of at least 190C(2F) to 970C(10F), preferably 290C(3F) to 870C(9F), particularly preferably 330C(3.5F) to 820C(8.5F), very particularly preferably 380C(4F) to 775C(8F), and most preferably 380C(4F) to 580C(6F) per millimole of the unsubstituted or at least monosubstituted monounsaturated or polyunsaturated cycloalkene and unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

[0076] In the method according to the present invention, electrochemical oxidation is preferably carried out with a constant current.

[0077] The current density for implementing the method according to the present invention is preferably at least 5 mA / cm². 2 , or at least 10mA / cm 2 , or at least 15mA / cm 2 , or at least 20mA / cm² 2 , or 20mA / cm 2 ~50mA / cm 2 Therefore, the reported surface area represents the geometric area of ​​the electrode.

[0078] A key advantage of the method according to the present invention is that the oxidizing agent used is electric current, which is a particularly environmentally friendly agent when it is obtained from renewable resources, i.e., particularly from biomass, solar thermal energy, geothermal energy, hydroelectric power, wind power, or especially photovoltaic power.

[0079] The method according to the present invention can be carried out over a wide temperature range, for example, 0°C to 60°C, preferably 5°C to 50°C, particularly preferably 10°C to 40°C, and most particularly preferably 15°C to 30°C.

[0080] The method according to the present invention can be carried out under high or low pressure. When the method according to the present invention is carried out under high pressure, a pressure of up to 16 bar is preferred, and a pressure of up to 6 bar is particularly preferred.

[0081] The method according to the present invention may also be carried out, preferably, at atmospheric pressure.

[0082] The products produced by the method of the present invention can be isolated / purified by conventional methods known to those skilled in the art, particularly by extraction, crystallization, centrifugation, precipitation, distillation, evaporation, or chromatography.

[0083] The method according to the present invention is preferably carried out without the addition of a catalyst, and in particular without the addition of a transition metal catalyst.

[0084] Similarly, the method according to the present invention is preferably carried out without the addition of any further oxidizing agent, except for oxygen or atmospheric oxygen. [Examples]

[0085] The following embodiments further illustrate the present invention, but do not limit its scope.

[0086] General information and methods Chemicals of analytical quality were obtained and used from commonly used suppliers (TCI, Aldrich, Acros, etc.). Oxygen was obtained as is from Nippon Gases Deutschland GmbH in Düsseldorf, Germany, at quality 2.5, and used without modification.

[0087] The electrode material used was glassy carbon (Sigradur® G, manufactured by HTW Hochtemperatur Werkstoffe GmbH in Tierhaupten, Germany).

[0088] High-performance liquid chromatography (LPC) was performed using a Shimadzu HPLC-MS instrument equipped with a SIL 20A HT autosampler, CTO-20AC column oven, two LC-20AD pump modules for eluent gradient adjustment, an SPD-M20A diode array detector, a CBM-20A system controller, and a Eurospher II 100-5 C18 column (150 × 4 mm, Knauer, Berlin). Eluent: acetonitrile (ACN) / water / formic acid (1 vol%) (from 10% ACN to 90% ACN in 10 minutes + 100% ACN in 10 minutes). Mass spectrometry was performed using a Shimadzu LCMS-2020 instrument manufactured by Shimadzu, Japan.

[0089] 1 H-NMR and 13 ¹¹C-NMR spectra were recorded at 25°C using a Bruker Advance II 400 instrument (400 MHz, 5 mm BBFO probe with Z gradient and ATM, SampleXPress60 autosampler, Analytische Messtechnik, Karlsruhe, Germany).

[0090] Gas chromatography analysis was performed using a Shimadzu GC-2025 instrument (Shimadzu Corporation, Japan) fitted with an HP 5MS column (Agilent Technologies, Santa Clara, California; length: 30m, inner diameter: 0.25mm, film thickness: 0.25μm, carrier gas: hydrogen). GC-MS measurements were performed using a Shimadzu GC-2010 instrument (Shimadzu Corporation, Japan) fitted with an HP-1 column (Agilent Technologies, Santa Clara, California; length: 30m, inner diameter: 0.25mm, film thickness: 0.25μm, carrier gas: helium). Sample preparation for GC analysis was performed by column filtration through 60M silica gel (0.04~0.063mm, Macherey-Nagel GmbH & Co.KG, Düren, Germany).

[0091] The non-divided Teflon® cells used in electrolysis are described in the following literature: (a) C. Gutz, B. Klockner, SRWaldvogel, Org. Process Res. Dev. 2016, pp. 20, 26-32; b) A. Kirste, G. Schnakenburg, F. Stecker, A. Fischer, SRWaldvogel, Angew. Chem. Int. Ed. 2010, pp. 49, 971-975; Angew. Chem. 2010, pp. 122, 983-987 (see SI). The full range of these cells is also commercially available as the IKA Screening System (IKA-Werke GmbH & Co. KG, Staufen, Germany). The electrode dimensions were 7cm × 1cm × 0.3cm.

[0092] The gases were introduced in a controlled manner using two models of Brooks Instrument BV 5850S ​​mass flow controllers (MFCs) from Wienendaal, Netherlands. One controller was used for oxygen introduction, and the other for nitrogen introduction. The controllers were controlled by Smart DDE and Matlab R2017b software. Volumetric flow rates were further monitored by a DK800 float principle flow meter from Krohne Messtechnik GmbH in Duisburg. In all experiments conducted, the overall volumetric flow rate remained constant at 20 mL / min. This is also the maximum achievable volumetric flow rate, although limited by the MFCs used. The ratio of the two gas volumetric flow rates was adjusted using the MFCs and their software. The following gas cylinders were used: oxygen 2.5 (Nippon Gases Deutschland GmbH, Düsseldorf) and nitrogen 4.8 (Westfalen AG, Münster), or nitrogen 5.0 (Nippon Gases Deutschland GmbH, Düsseldorf). The gas distributor and gas inlet cover for the electrolytic cell were described in the literature (M. Dorr, D. Waldmann, SRWaldvogel, GIT Labor-Fachz, 2021, pp. 7-8, 26-28) and purchased from IKA (IKA-Werke GmbH & Co.KG, Hohenstaufen, Germany).

[0093] General Procedure GP1 In a 5 mL non-divided Teflon® pot cell, cycloalkanes (0.1-0.5 mmol), cycloalkenes (0.5-0.9 mmol, with a total of 1 mmol of alkanes and alkenes), and tetrabutylammonium nitrate (0.5 equivalents) were initially added and dissolved in acetonitrile or isobutyronitrile (5 mL). Glassy carbon electrodes were attached to the cell at 0.5 cm intervals. The immersion surface area of ​​the electrodes was 1.8 cm². 2 The cell was fixed to a stainless steel block, and the temperature was 22°C with a current density of 10 mA / cm². 2 Constant current electrolysis was performed.

[0094] The amount of charge used was based on the theoretical charge for the oxidation of each component, depending on the ratio of the two components (alkane / alkene = 0.1 / 0.9: 7.6F, 0.25 / 0.75: 7.0F, 0.5 / 0.5: 6.0F). After electrolysis, 1,3,5-trimethoxybenzene (10 mg) was added to the reaction solution as an internal standard. Three drops were taken and filtered through 60 M silica gel (eluent: ethyl acetate). The filtrate was collected in a GC vial and subjected to GC analysis. The remaining reaction solution was first desoldered by distillation. Next, the conductive salt was removed by extraction using 10 mL of ethyl acetate and 10 mL of aqueous HCl (0.1 M). The solvent of the organic phase was removed by distillation, and the residue was placed in aqueous NaOH (1 M, 10 mL). The aqueous phase was washed with 10 mL of diethyl ether. After phase separation, the aqueous phase was adjusted to pH 1 with HCl aqueous solution (1M), and this phase was extracted with 2 × 10 mL of ethyl acetate. The organic phase was dried with sodium sulfate, and after removing the solvent by distillation, the dicarboxylic acid product was dried under high vacuum.

[0095] After the charge was used, 10 mg of 1,3,5-trimethoxybenzene was added to the reaction solution as an internal standard. Three drops of the reaction solution were taken and analyzed by gas chromatography, and the products were quantified. These were eluted with ethyl acetate and approximately 330 mg of 60 M silica gel. Approximately 1.5 mL of the filtrate was collected in a GC vial, and the oxidation products were examined by GC-FID and GC-MS. Quantification was performed by pre-calibration of the gas chromatograph.

[0096] Experimental Example 1 The following co-electrolysis was performed according to GP1 (Scheme 1, Table 1).

[0097] [ka]

[0098] [Table 1]

[0099] For n=3, acetonitrile was used as the solvent, and for n=7, isobutyronitrile was used as the solvent. Cumulative charge amounts for A and B: a) 7.6F; b) 7.0F; c) 6.0F; d) Measurement by external GC calibration (internal standard: 1,3,5-trimethoxybenzene); e) Yield after isolation. All yields are related to the molar amount of the particular reactant used.

Claims

1. A method for producing an unsubstituted or at least monosubstituted α,ω-dicarboxylic acid or an unsubstituted or at least monosubstituted ketocarboxylic acid and an unsubstituted or at least monosubstituted cycloalkanone by electrochemical oxidation, (a-1) A step of preparing at least one unsubstituted or at least one substituted monounsaturated cycloalkene or an unsubstituted or at least one substituted polyunsaturated cycloalkene, (a-2) A step of preparing at least one unsubstituted or at least one monosubstituted saturated alicyclic hydrocarbon, The substituents of the monounsaturated or polyunsaturated cycloalkene and the substituents of the saturated alicyclic hydrocarbon are each independently selected from the group consisting of methyl, phenyl, or benzyl. The phenyl or benzyl substituents themselves are either unsubstituted or F, Cl, Br, and NO, respectively. ２ Each substituent is independently selected from the group consisting of the above, and is either monosubstituted or polysubstituted. The number of ring members in the cycloalken obtained in step (a-1) and the alicyclic hydrocarbon obtained in step (a-2) are the same. (b) A step of preparing at least one inorganic or organic nitrate, The nitrate in step (b) above is a cation of the general formula [ ＋ ] [NO ３ － It exists as a nitrate of ] The [cation of the general formula ＋ is Na ＋ , K ＋ , and the general structure [R １ R ２ R ３ R ４ N ＋ (wherein R １ , R ２ , R ３ and R ４ are each independently selected from the group consisting of C １ -C １６ alkyl). An ammonium ion having General structure (I): 【Chemistry 1】 (In the formula, R １ and R ２ C is a straight-chain or branched-chain C １ ~C １８ Each is independently selected from the group consisting of alkyls, R ３ H and linear or branched C １ ~C １８ (Selected from the group consisting of alkyl groups.) The imidazolium cation, General structure (II): 【Chemistry 2】 (In the formula, R １ C １ ~C １８ Selected from the group consisting of alkyl groups, R ２ , R ３ and R ４ H and linear or branched C １ ~C １８ A pyridinium cation and a general structure [R] are independently selected from the group consisting of alkyl groups. １ａ R ２ａ R ３ａ R ４ａ P ＋ ] (wherein, R １ａ , R ２ａ , R ３ａ , R ４ａ C １ ~C １６ Each is independently selected from the group consisting of alkyl groups. Selected from the group consisting of phosphonium ions, (c) In an electrolytic cell in a reaction medium containing oxygen, electrochemically oxidize the unsubstituted or at least one-substituted monounsaturated cycloalkene or unsubstituted or at least one-substituted polyunsaturated cycloalkene prepared in step (a-1) and the unsubstituted or at least one-substituted saturated alicyclic hydrocarbon prepared in step (a-2) in the presence of the inorganic or organic nitrate prepared in step (b). Methods that include...

2. The aforementioned unsubstituted or at least one-substituted monounsaturated cycloalkene or unsubstituted or at least one-substituted polyunsaturated cycloalkene is monocyclic or bicyclic, The unsubstituted or at least monosubstituted monounsaturated monocyclic cycloalkenes or unsubstituted or at least monosubstituted polyunsaturated monocyclic cycloalkenes are either unsubstituted or monosubstituted or polysubstituted with substituents independently selected from the group consisting of methyl, phenyl, or benzyl, respectively, and the phenyl or benzyl substituents themselves are either unsubstituted or F, Cl, Br, and NO, respectively. ２ They are monosubstituted or polysubstituted with substituents independently selected from the group consisting of and / or The aforementioned unsubstituted or at least one-substituted monounsaturated bicyclic cycloalkenes or unsubstituted or at least one-substituted polyunsaturated bicyclic cycloalkenes have 7 to 18 carbon atoms in the ring system, which are either unsubstituted or monosubstituted or polysubstituted with substituents independently selected from the group consisting of methyl, phenyl, or benzyl, respectively, and the phenyl or benzyl substituents themselves are either unsubstituted or F, Cl, Br, and NO, respectively. ２ The method according to claim 1, wherein the substituents are monosubstituted or polysubstituted with substituents independently selected from the group consisting of the above.

3. The aforementioned unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons are monocyclic or bicyclic, The monocyclic or bicyclic saturated alicyclic hydrocarbon has 5 to 18 carbon atoms in its ring system and is either unsubstituted or monosubstituted or polysubstituted with substituents independently selected from the group consisting of methyl, phenyl, or benzyl, where the phenyl or benzyl is either unsubstituted or F, Cl, Br, and NO, respectively. ２ The method according to claim 1, wherein each substituent may be monosubstituted or polysubstituted with a substituent independently selected from the group consisting of the above.

4. The aforementioned unsubstituted or at least monosubstituted saturated alicyclic hydrocarbons are The method according to claim 1, wherein the monocyclic saturated hydrocarbon has 6 to 12 carbon atoms in the ring, and is either unsubstituted or monosubstituted or polysubstituted with substituents independently selected from the group consisting of methyl, phenyl, or benzyl.

5. The method according to claim 1, wherein the cycloalkene is selected from the group consisting of cyclohexene, cycloheptene, cyclooctene, cyclononene, cyclodecene, cycloundecene, cyclododecene, 1-phenylcyclohexa-1-ene, bicyclo[2.2.1]hept-2-ene, α-pinene, and carene, and the saturated alicyclic hydrocarbon is selected from the group consisting of cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane.

6. The method according to claim 1, wherein the preparation of at least one unsubstituted or at least one substituted monounsaturated cycloalkene or an unsubstituted or at least one substituted polyunsaturated cycloalkene by step (a-1) and the provision of at least one unsubstituted or at least one substituted saturated alicyclic hydrocarbon by step (a-2) are carried out in combination.

7. The method according to claim 1, wherein the molar ratio of the unsubstituted or at least one-substituted monounsaturated cycloalkene or unsubstituted or at least one-substituted polyunsaturated cycloalkene is in any case 40 to 95 mol% of the total amount of the unsubstituted or at least one-substituted monounsaturated cycloalkene or unsubstituted or at least one-substituted polyunsaturated cycloalkene and the unsubstituted or at least one-substituted saturated alicyclic hydrocarbon used.

8. The method according to claim 1, wherein the molar ratio of the unsubstituted or at least one-substituted monounsaturated cycloalkene or unsubstituted or at least one-substituted polyunsaturated cycloalkene is, in any case, greater than 60 mol% of the total amount of the unsubstituted or at least one-substituted monounsaturated cycloalkene or unsubstituted or at least one-substituted polyunsaturated cycloalkene used and the unsubstituted or at least one-substituted saturated alicyclic hydrocarbon.

9. The method according to claim 1, wherein in the imidazolium cation of the general formula (I), radicals R1 and R2 are selected from the group consisting of linear or branched C1 to C18 alkyl groups, and R3 is hydrogen.

10. In the pyridinium cation of the general formula (II) above, radical R １ C is a straight-chain or branched-chain C １ ~C １８ It is alkyl, and radical R ２ , R ３ and R ４ C is a straight-chain or branched-chain C １ ~C ８ The method according to claim 1, wherein each is independently selected from the group consisting of alkyl groups.

11. The method according to claim 1, wherein the organic nitrate is selected from the group consisting of tetra-n-butylammonium nitrate, methyltri-n-octylammonium nitrate, tetra-n-butylphosphonium nitrate, methyltri-n-octylphosphonium nitrate, and 1-butyl-3-methylimidazolium nitrate.

12. The method according to claim 1, wherein the reaction medium is a polar aprotic reaction medium mixed with water, and the polar aprotic reaction medium is selected from the group consisting of aliphatic nitriles, aliphatic ketones, alicyclic ketones, dialkyl carbonates, cyclic carbonates, lactones, aliphatic nitroalkanes, dimethyl sulfoxides, esters and ethers, or at least two combinations thereof.

13. The method according to claim 1, wherein the reaction medium is a polar aprotic reaction medium mixed with water, and the water content is in all cases a maximum of 20% by volume of the total amount of the reaction medium.

14. The method according to claim 1, wherein the reaction medium is a polar aprotic reaction medium selected from the group consisting of acetonitrile, isobutyronitrile, adiponitrile, acetone, dimethyl carbonate, methyl ethyl ketone, 3-pentanone, cyclohexanone, nitromethane, nitropropane, tert-butyl methyl ether, dimethyl sulfoxide, γ-butyrolactone, and ε-caprolactone, or at least two combinations thereof, and in any case exists mixed with water.

15. The method according to claim 1, wherein the reaction medium includes a solubilizing component that enables one or more other substances to dissolve.

16. The method according to claim 15, wherein the solubilizing component is a primary alcohol, a secondary alcohol, a monoketone or a dialkyl carbonate, or a mixture of at least two of these components, and is present in a mixture with water.

17. aliphatic C １－６ The method according to claim 15, wherein alcohol is present as one or more solubilizing components and is mixed with water.

18. The reaction medium is dimethyl carbonate, and contains at least one C １－６ The method according to claim 1, wherein the alcohol is present in a mixed state.

19. The method according to claim 18, wherein the reaction medium includes water.

20. The method according to claim 15, wherein one or more solubilizing components are present in an amount of less than 50% by volume relative to the total amount of the reaction medium.

21. The method according to claim 1, wherein the inorganic or organic nitrate is used in an amount of 0.1 to 2.0 equivalents with respect to the amount of unsubstituted or at least monosubstituted monounsaturated cycloalkene or unsubstituted or at least monosubstituted polyunsaturated cycloalkene used, or in an amount of 0.8 to 10.0 equivalents with respect to the amount of unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

22. The method according to claim 1, wherein an oxygen-containing gas atmosphere is provided in spatial communication with the reaction medium.

23. The method according to claim 1, wherein the gas atmosphere is air.

24. The method according to claim 1, wherein gas exchange between the gas atmosphere and the reaction medium is performed by introducing the gas atmosphere into the reaction medium or by stirring the reaction medium in the presence of the gas atmosphere.

25. The method according to claim 24, wherein stirring the reaction medium is used to control the electrochemical oxidation.

26. The method according to claim 1, wherein the amount of oxygen dissolved in the reaction medium is at least 1 millimol / L.

27. The method according to claim 1, wherein oxygen or atmospheric oxygen is removed and no further oxidizing agent is added.

28. The method according to claim 1, wherein the electrolytic cell is a non-divided cell in which the anode and cathode are arranged in the same compartment without being separated.

29. The method according to claim 1, wherein the electrolytic cell comprises a glassy carbon anode, a graphite anode, or a BDD anode.

30. The method according to claim 1, wherein the electrolytic cell comprises a glassy carbon cathode, a graphite cathode, or a BDD cathode.

31. The method according to claim 1, wherein the distance between electrodes in the electrolytic cell is 0.1 mm to 2.0 cm.

32. The method according to claim 1, wherein the amount of charge used for the electrochemical oxidation is at least 190 C (2 F (F: Faraday constant)) to 970 C (10 F (F: Faraday constant)) per millimoles of unsubstituted or at least monosubstituted monounsaturated cycloalkene or unsubstituted or at least monosubstituted polyunsaturated cycloalkene and unsubstituted or at least monosubstituted saturated alicyclic hydrocarbon used.

33. The method according to claim 1, wherein the electrochemical oxidation is carried out with a constant current.

34. The current density is at least 5 mA / cm². ２ The method according to claim 1, wherein the surface area represents the geometric area of ​​the electrode.

35. The current density is at least 20 mA / cm². ２ ~50 mA / cm ２ The method according to claim 1, wherein the surface area represents the geometric area of ​​the electrode.

36. The method according to claim 1, wherein the current used in the electrochemical oxidation is obtained from renewable resources.

37. The method according to claim 1, wherein the electrochemical oxidation is carried out at a temperature in the range of 0°C to 60°C.

38. The method according to claim 1, performed under atmospheric pressure.

39. The method according to claim 1, which is carried out under reduced pressure, which is lower than atmospheric pressure.

40. The method according to claim 1, which is carried out under high pressure, which is higher than atmospheric pressure.

41. The method according to claim 1, performed in a batch manner.

42. The method according to claim 1, which is carried out without adding a catalyst.

43. The method according to claim 1, which is carried out continuously within a non-divided flow-through electrolytic cell.

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